﻿using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

namespace Wiki.WinClient
{
    /// <summary>
    /// Summary description for BitmapRegion.
    /// </summary>
    public class BitmapRegion
    {
        public BitmapRegion()
        { }
        /// <summary>
        /// Create and apply the region on the supplied control
        /// 创建支持位图区域的控件（目前有button和form）
        /// </summary>
        /// <param name="control">The Control object to apply the region to控件</param>
        /// <param name="bitmap">The Bitmap object to create the region from位图</param>
        public static void CreateControlRegion(Control control, Bitmap bitmap)
        {
            // Return if control and bitmap are null
            if (control == null || bitmap == null)
                return;

            // Set our control''s size to be the same as the bitmap
            control.Width = bitmap.Width;
            control.Height = bitmap.Height;
            // Check if we are dealing with Form here
            if (control is System.Windows.Forms.Form)
            {
                // Cast to a Form object
                Form form = (Form)control;
                // Set our form''s size to be a little larger that the  bitmap just
                // in case the form''s border style is not set to none in the first place
                form.Width = control.Width;
                form.Height = control.Height;
                // No border
                form.FormBorderStyle = FormBorderStyle.None;
                // Set bitmap as the background image
                form.BackgroundImage = bitmap;
                // Calculate the graphics path based on the bitmap supplied
                GraphicsPath graphicsPath = CalculateControlGraphicsPath(bitmap);
                // Apply new region
                form.Region = new Region(graphicsPath);
            }
            // Check if we are dealing with Button here
            else if (control is System.Windows.Forms.Button)
            {
                // Cast to a button object
                Button button = (Button)control;
                // Do not show button text
                button.Text = "";

                // Change cursor to hand when over button
                button.Cursor = Cursors.Hand;
                // Set background image of button
                button.BackgroundImage = bitmap;

                // Calculate the graphics path based on the bitmap supplied
                GraphicsPath graphicsPath = CalculateControlGraphicsPath(bitmap);
                // Apply new region
                button.Region = new Region(graphicsPath);
            }
        }
        /// <summary>
        /// Calculate the graphics path that representing the figure in the bitmap
        /// excluding the transparent color which is the top left pixel.
        /// //计算位图中不透明部分的边界
        /// </summary>
        /// <param name="bitmap">The Bitmap object to calculate our graphics path from</param>
        /// <returns>Calculated graphics path</returns>
        private static GraphicsPath CalculateControlGraphicsPath(Bitmap bitmap)
  {
   // Create GraphicsPath for our bitmap calculation
   GraphicsPath graphicsPath = new GraphicsPath();
   // Use the top left pixel as our transparent color
   //使用左上角的一点的颜色作为我们透明色
   Color colorTransparent = bitmap.GetPixel(0, 0);
   // This is to store the column value where an opaque pixel is first found.
   // This value will determine where we start scanning for trailing opaque pixels.
   //第一个找到点的X
   int colOpaquePixel = 0;
   // Go through all rows (Y axis)
   // 偏历所有行（Y方向）
   for(int row = 0; row < bitmap.Height; row ++)
   {
    // Reset value
    colOpaquePixel = 0;
    // Go through all columns (X axis)
    for(int col = 0; col < bitmap.Width; col ++)
    {
     // If this is an opaque pixel, mark it and search for anymore trailing behind
     //如果是不需要透明处理的点则标记，然后继续偏历
     if(bitmap.GetPixel(col, row) != colorTransparent)
     {
      // Opaque pixel found, mark current position
      //记录当前
      colOpaquePixel = col;
      // Create another variable to set the current pixel position
      //建立新变量来记录当前点
      int colNext = col;
      // Starting from current found opaque pixel, search for anymore opaque pixels
         // trailing behind, until a transparent   pixel is found or minimum width is reached
      ///从找到的不透明点开始，继续寻找不透明点,一直到找到或则达到图片宽度
      for(colNext = colOpaquePixel; colNext < bitmap.Width; colNext ++)
      if(bitmap.GetPixel(colNext, row) == colorTransparent)
      break;
      // Form a rectangle for line of opaque   pixels found and add it to our graphicspath
      //将不透明点加到graphics path
      graphicsPath.AddRectangle(new Rectangle(colOpaquePixel, row, colNext -colOpaquePixel, 1));
      // No need to scan the line of opaque pixels just found
      col = colNext;
     }
    }
   }
   // Return calculated graphics path
   return graphicsPath;
  }
    }
}